Laboratory fume hood

ABSTRACT

An adjustable sash assembly for use with fume hoods and the like, said sash assembly comprising three generally rectangular sash members which are slidably mounted for vertical adjustment and which define a face opening for passage of room or auxiliary air into a fume hood. Two of the sash members are interconnected by way of a pulley mechanism which automatically provides a constant face opening for several sash positions defining access openings through which a user may reach into the interior of the fume hood. One of the pulley-connected sashes may be selectively tilted outwardly to entrain additional air from an auxiliary supply.

United States Patent Worick, Jr. [451 A r. 10 1973 [54] LABORATORY FUME HOOD [76] Inventor: Ralph E. Worick, Jr., 264 North Primary Exami'fer Meyer Peru Liberty Street, Delaware, Ohio Assistant Exammer-Ronald C. Capossela 43015 Attorney-Clarence A. OBrien et al.

[22] Filed: July 19, 1971 57 ABSTRACT Appl. No.: 163,773

An adjustable sash assembly for use with fume hoods and the like, said sash assembly comprising three generally rectangular sash members which are slidably mounted for vertical adjustment and which define a face opening for passage of room or auxiliary air into a fume hood. Two of the sash members are interconnected by way of a pulley mechanism which automatically provides a constant face opening for several sash positions defining access openings through which a user may reach into the interior of the fume hood. One of the pulley-connected sashes may be selectively tilted outwardly to entrain additional air from an auxiliary supply.

6 Claims, 7 Drawing Figures LABORATORY FUME noon The present invention is generally related to fume hoods and, more particularly to laboratory fume hoods with adjustable closures.

In the past, many laboratory fume hoods have been provided with adjustable closures. However, such constructions, for the most part, have been inadequate for the reason that closure adjustment changed the area of the face opening causing significant changes in the linear face velocity, often resulting in the escape of fumes into the laboratory. If the closure was adjusted to reduce the opening to a minimum, say for working through a bottom opening, the reduction in the face opening area created intolerable high face velocities. Contrastingly, when the closure was adjusted for maximum opening, the face velocity was reduced to unacceptable levels, such that fumes often escaped into the laboratory. In order to correct such changes in face velocity, it was necessary to provide dampers, baffles,

airfoils, bypass openings, or the like. As such, operation of such fume hoods became complex and inconvenient to use. Furthermore, the additional mechanisms required to maintain constant face velocities greatly increased the overall cost of the fume hood construction.

It is an object of the present invention to provide a novel fume hood sash assembly which is vertically adjustable to allow access into the fume hood at different vertical positions, yet maintain a constant face opening and, thus, a substantially constant face velocity without the use of adjustable baffles or the like.

Another object of the present invention is to provide a unique sash assembly for fume hoods and the like, said assembly including a pair of vertically slidable sash members connected together by a pulley mechanism, such that movement of one sash member produces a corresponding movement of the other in the opposite direction, each sash member serving as a counterbalance for the other.

It is a further object of the present invention to provide a versatile sash assembly comprising a plurality of slidably mounted sash members, one of which may be selectively tilted outwardly to entrain the flow of air from an auxiliary air supply.

Still another object of the present invention is to provide a fume hood sash assembly including a means for providing constant face velocity for different closure positions as well as means for entraining air from an auxiliary air supply, yet which requires a minimum number of parts and is relatively inexpensive to manufacture.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout, and in which:

FIG. 1 is a front elevational view of a fume hood with the sash assembly of the present invention.

FIG. 2 is a sectional view of the fume hood and sash assembly of the present invention with one of the sash members tilted outwardly to entrain auxiliary air.

FIGS. 3, 4 and 5 are sectional view of the sash assembly with the respective sash members located in different positions. v

FIG. 6 is a partial perspective view illustrating the connection between the center sash member and the sash support post.

FIG. 7 is a partial perspective view illustrating the connection between the tiltable sash member and the sash support post.

Referring now, more particularly, to FIGS. 1 and 2, a typical fume hood associated with the present invention is generally indicated by the numeral 10 and includes an exhaust duct 12 and an auxiliary air outlet 14 located at the top thereof together with a lighting fixture 15. The lower section of the fume hood is comprised of a bench portion 16 which supports a horizontal work table 18 extending into the interior of the fume hood. A pair of sash support posts 20 extend vertically along opposite sides of the fume hood and slidably receive three sash members 24, 26 and 28. Each support post is formed to provide three vertical mounting channels, each of which is adapted to accommodate one of the sash members. Each of the center channels is provided with a plurality of vertically spaced apertures 29 which serve to position the center sash member 26 as hereinafter explained.

Sash members 24 and 28 are interconnected by way of a flexible chain, rope or cable 30 extending around a rotatably mounted pulley 32, located at the top of each vertical support post. As such, upward movement of sash member 28 produces a corresponding downward movement of sash member 24. Furthermore, sashes 24 and 28 tend to counterbalance each other, eliminating the need for counter weights, springs and the like. Each sash member is generally rectangular in shape and, preferably, is provided with a transparent surface area 33 of safety glass or the like which permits observation of the fume hood interior area and also aids in the lighting thereof. Sash member 28 is illustrated in FIGS. 1 and 2 in the tilted position and resting against a pair of support arms 34 each rigidly affixed to one of the support posts. When in the tilted position, sash member 28 serves to entrain a flow of auxiliary air emanating from the opening of auxiliary air supply 14. Thus, it will be appreciated that the sash assembly of the present invention not only provides for constant face velocity, as hereinafter explained, but, also, provides a means for entraining the flow of auxiliary air.

Sash member 28 is provided with a pair of longitudinally extending tabs 36 at the opposite ends of the top edge thereof. As the sash member is moved from the titled position to the vertical position, tabs 36 pass through slotted openings 38 formed in each support post. A pair of rotatably mounted lock members 40 are provided for selectively closing the slotted openings 38 when sash member 28 is in the vertical position.

Referring to FIG. 7, the details of the tiltable sash member mounting may be more fully appreciated. A mounting pin 42 is rigidly affixed to sash member 28 near its bottom corners. The ends of cables 30 are fastened to mounting pins 42 for transferring movement to the sash member. Thus, it is appreciated that one of the pully-connected sash members is mounted for convenient outward tilting, as well as vertical positioning.

Referring to FIG. 6, it can be seen that the center sash member 26 is provided with a positioning pin mechanism 44 including a spring biased pin member 46 adapted to fit into mounting apertures 29 to selectively position the sash member. As such, sash member 26 may be located in any one of the four vertical positions defined by mounting apertures 29. Of course, other conventional fastening means may be used, if desired.

It should be noted that the fume hood is provided with an opening confronting and immediately adjacent to the sash assembly. The opening is generally rectangular in shape, having a width not greater than the width of each sash member, and a height not to exceed that of the combined vertical dimensions of all three sash members. As such, the sash members are capable of substantially closing off the entrance opening of the fume hood when they are vertically staggered, as illustrated in FIG. 5.

The more important aspect of the present invention, however, is that the pulley-connected sash members may be moved to provide different vertical access openings without changing the effective face opening area. The importance of this feature cannot be overemphasized. When using fume hoods, the nature of the work often demands that the technician have access to the fume hood interior through a lowermost access opening close to the work table. On other occasions, the technician may be required to seek access through an opening located higher in the fume hood. With conventional fume hoods having adjustable closures, a change in the access opening location produced undesirable changes in the face velocity of the air passing therethrough. Conventional face velocity adjustment means, such as baffles, were a great inconvenience to the laboratory technician, especially when time was of the essence. With the sash assembly of the present invention, however, this is eliminated.

FIG. 3 illustrates the sash members positioned-to provide a lowermost access opening of an area approximately equal to that ofa single sash member. When it is desired to seek access through a higher location in the fume hood, sash member 28 is pulled in the downward direction until it arrives at a lowermost position as illustrated in FIG. 4. It will be appreciated that in this position, the sash assembly face opening is of the same area as that provided by lower access opening illustrated in FIG. 3. Also, throughout the movement of the sash members, the combined areas of the face openings remain constant. Thus, it is possible to provide two relatively narrow access openings, when the condition demands such, yet, at the same time provide a constant area face velocity opening. This operation is achieved by the fact that the sash support post extends vertically above and beyond the fume hood opening by a distance at least as great as the vertical dimension of each sash member. Thus, as sash member 24 is moved upwardly from the position shown in FIG. 3, it has no affect upon the face opening since it is moved into an area which does not confront the fume hood opening. At the same time, sash member 26 is in a position which overlaps sash member 24 in its original position, such that this area is maintained in the closed condition. It will be appreciated that the unique relationship between the sash members, the sash support posts and the fume hood opening provides a means of automatically maintaining constant face opening, and, thus, constant face velocity. Furthermore, during the above-described movement, the pulley-connected sashes counterbalance each other providing an infinite number of vertical positions without the need for fastening means.

It should be understood that when the sash assembly of the present invention is utilized in the positions illustrated in FIGS. 3-5, the cleaning or fume removing air flow is drawn from the surrounding laboratory or room. If, however, it is required to provide a larger access opening or if the laboratory layout demands such, the auxiliary air supply 14 may be utilized to maintain the face velocity within desirable limits to assure against the escape of fumes from the hood. This is done by placing sash member 28 in the tilted position, as illustrated in FIGS. 1 and 2 and as explained above. Thus, the unique interconnection between the sash members not only assures constant face velocity, but, also provides for the entrainment of auxiliary air when an extra large access opening is required.

It will be appreciated that the sash assembly of the present invention provides for relatively simple sash member movement without the need for counterbalancing weights or springs, or the use of exterior cables and weights. Furthermore, since each sash member is transparent, the full height of the sash assembly permits fume hood lighting from exterior sources. The sash assembly may be easily adjusted to furnish multiple panes of safety glass for the ultimate protection of the laboratory technician. Also, each sash member may be easily cleaned without removal and without the requirement of entrance into the fume hood proper. The sash assembly includes a minimum number of parts, is extremely compact and may be installed on existing fume hoods with a minimum amount of work.

It should be noted that minor changes in the shape or materials of the sash members or their exact location relative to the fume hood opening are deemed to fall within the scope of the present invention. Furthermore, it is foreseeable that the sash assembly of the present invention may be provided with a total number of sash members greater than that illustrated in the drawings, and that the relative position of the sash members in the mounting channels may be varied.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

What is claimed as new is as follows:

1. A sash assembly in combination with a fume hood having a frontal opening for the passage of fume removing air, said frontal opening being generally rectangular in shape and having a first vertical dimension, said sash assembly including support means adjacent said frontal opening and a plurality of rectangular sash members supported by said support means, said support means including pulley means connecting first and second of said plurality of sash members to provide simultaneous selective movement thereof in opposite vertical directions, said first and second sash members each being of a second vertical dimension, said support means defining a vertical path of travel for said first and second sash members extending vertically beyond said frontal opening by a distance approximately equal to said second vertical dimension, said plurality of sash members including a third sash member, said frontal opening first vertical dimension being approximately equal to the composite vertical dimension of said first, second, and third sash members, said frontal opening including lower, middle, and upper rectangular frontal areas corresponding to lower, middle, and upper sash positions, said third sash being selectively positionable in said upper position, and said pulley means being such that said first sash member is in said upper position when said second sash member is in said middle position to define a face opening of predetermined area, said area remaining constant when said third sash member is in said upper position as said first and second sash members are moved simultaneously with said first sash member moving upward into the vertical path extension as said second sash member is moved toward said lower position, thereby providing constant face velocity for the air entering said fume hood while changing the location of said opening from said lower position to said middle position.

2. The structure set forth in claim 1 wherein one of said support means includes means permitting pivotal tilting of one of said first and second sash members from its vertical orientation to an angular position for the entrainment of air flow.

3. The structure set forth in claim 2 wherein said fume hood includes auxiliary air means for directing a flow of auxiliary air in the downward direction toward said tiltable sash member when in the tilted angular position, such that the auxiliary air is entrained into said fume hood.

4. The structure set forth in claim 1 wherein said third sash member is selectively positionable in said middle position, said area remaining constant when said third sash member is in said middle position as said first and second sash members are moved simultaneously with said first sash member moving upward into the vertical path extension as said second sash member is moved toward said lower position, thereby providing constant face velocity for the air entering said fume hood while changing the location of said opening from said lower position to said middle position.

5. The structure set forth in claim 4 wherein one of said support means includes means permitting pivotal tilting of one of said first and second sash members from its vertical orientation to an angular position for the entrainment of air flow.

6. The structure set forth in claim 5 wherein said fume hood includes auxiliary air means for directing a flow of auxiliary air in the downward direction toward said tiltable sash member when in the tilted angular position, such that the auxiliary air is entrained into said fume hood. 

1. A sash assembly in combination with a fume hood having a frontal opening for the passage of fume removing air, said frontal opening being generally rectangular in shape and having a first vertical dimension, said sash assembly including support means adjacent said frontal opening and a plurality of rectangular sash members supported by said support means, said support means including pulley means connecting first and second of said plurality of sash members to provide simultaneous selective movement thereof in opposite vertical directions, said first and second sash members each being of a second vertical dimension, said support means defining a vertical path of travel for said first and second sash members extending vertically beyond said frontal opening by a distance approximately equal to said second vertical dimension, said plurality of sash members including a third sash member, said frontal opening first vertical dimension being approximately equal to the composite vertical dimension of said first, second, and third sash members, said frontal opening including lower, middle, and upper rectangular frontal areas corresponding to lower, middle, and upper sash positions, said third sash being selectively positionable in said upper position, and said pulley means being such that said first sash member is in said upper position when said second sash member is in said middle position to define a face opening of predetermined area, said area remaining constant when said third sash member is in said upper position as said first and second sash members are moved simultaneously with said first sash member moving upward into the vertical path extension as said second sash member is moved toward said lower position, thereby providing constant face velocity for the air entering said fume hood while changing the location of said opening from said lower position to said middle position.
 2. The structure set forth in claim 1 wherein one of said support means includes means permitting pivotal tilting of one of said first and second sash members from its vertical orientation to an angular position for the entrainment of air flow.
 3. The structure set forth in claim 2 wherein said fume hood includes auxiliary air means for directing a flow of auxiliary air in the downward direction toward said tiltable sash member when in the tilted angular position, such that the auxiliary air is entrained into said fume hood.
 4. The structure set forth in claim 1 wherein said third sash member is selectively positionable in said middle position, said area remaining constant when said third sash member is in said middle position as said first and second sash members are moved simultaneously with said first sash member moving upward into the vertical path extension as said second sash member is moved toward said lower position, thereby providing constant face velocity for the air entering said fume hood while changing the location of said opening from said lower position to said middle position.
 5. The structure set forth in claim 4 wherein one of said support means includes means permitting pivotal tilting of one of said first and second sash members from its vertical orientation to an angular position for the entrainment of air flow.
 6. The structure set forth in claim 5 wherein said fume hood includes auxiliary air means for directing a flow of auxiliary air in the downward direction toward said tiltable sash member when in the tilted angular position, such that the auxiliary air is entrained into said fume hood. 